This invention relates to fluid flow control and, more specifically, to systems and techniques for effecting a substantially continuous irrigation of crops.
Crop irrigation for many years has been carried out by so-called furrow and sprinkler techniques wherein water is applied to the crops in relatively large doses at prescribed intervals. It will be appreciated that the availability of water in the soil can gradually diminish from one watering to the next. This is an important consideration since most plant roots, especially those of sugarcane plants for example, can undergo considerable stress and strain when attempting to extract moisture from water-deficient soil. It has been found that such strain can adversely affect the ultimate crop yield at harvest.
An irrigation technique which is rapidly gaining wide use among sugarcane growers is the so-called "drip" or "trickle" method which greatly relieves root stress. This technique is carried out by a network of conduits placed adjacently to plant rows. The conduits, which can be laid above or below ground, are provided with tiny openings spaced longitudinally therealong. In practice, water is continuously supplied to the conduits to effect a continuous drip or trickle of water through the openings. Water is thus distributed to the soil in a continuous fashion to eliminate periods where the soil is overly dry. The plants are thereby constantly presented with an ample water supply, as is reflected in increased harvest yields.
Among the problems characteristic of drip irrigation techniques is a tendency for the drip openings to become clogged. Such an occurrence is not surprising considering that the size of the opening can run as small as or smaller than 0.51 mm. in diameter. Consequently, the openings are susceptible to being blocked by solids such as soil particles, plant fibers, algae and various micro-organisms characteristic of practically all water sources. Filtering of the water has been found effective in screening out relatively large particles, but particles that are too small to be filtered by present techniques can accumulate around the drip openings and eventually block them.
One measure that has proven successful in preventing clogging by such particle accumulation is the practice of periodically flushing the drip conduits. This is accomplished by opening the remote ends of the drip conduits to allow the water to flow rapidly through the conduits. This high velocity flow tends to scrub away solid accumulations that may have been built-up around the drip openings.
It is common to effect flushing by manual actuation of flushing valves that are attached at the remote ends of the drip conduits. Due to the high number of conduits deployed in a typical crop field, such manual manipulation is not economically efficient.
In an attempt to reduce labor costs, it has been proposed to utilize valves of the pressure responsive type which automatically open upon sensing a change in the water pressure present in the drip conduit. Specific proposals include the suggested employment of valves which open in response to increased water pressure, as well as valves which open in response to reduced water pressure. Both types of valves, however, involve significant shortcomings in the present environment. For example, it is usually very costly to effect an increase in water pressure. On the other hand, flushing by reduced water pressure is not as efficient since the scrubbing action in the drip conduit is less intense.
It is, therefore, an object of the present invention to provide novel methods and apparatus for alleviating or overcoming problems like those previously discussed.
It is another object of the present invention to provide novel methods and apparatus by which both drip irrigation and drip-tube flushing can be conveniently performed under high water pressure conditions.
One other object of the invention is to provide such novel methods and apparatus in which a network of drip tubes are flushed simultaneously by remote control, absent the need for varying pressure in the water distribution lines or for manually opening each drip tube.
A further object of the invention is to provide such novel methods and apparatus which rely solely upon irrigation liquid as a source of actuating power.
A further object of the invention is to provide a novel pressure-responsive sealing valve assembly which is of simplistic construction and highly water resistant.